1. Field of the Invention
The embodiments relate to a nonvolatile memory device and a method of driving the same, and more particularly, to a nonvolatile memory device and a method of driving the same, which adopt an improved write operation.
2. Description of the Prior Art
A nonvolatile memory device using a resistance material includes a phase change random access memory (PRAM), a resistive RAM (RRAM), a magnetic RAM (MRAM), and the like. A dynamic RAM (DRAM) or a flash memory device stores data using charges, whereas the nonvolatile memory device using the resistance material stores data using a phase change of a phase change material such as a chalcogenide alloy (in the case of a PRAM), a resistance change of a variable resistance material (in the case of an RRAM), a resistance change of a magnetic tunnel junction (MTJ) thin film according to a magnetization state of a ferromagnetic material (in the case of an MRAM), and the like.
More specifically, the PRAM stores data using a phase change material such as a chalcogenide alloy of which the phase is changed to a crystalline state or an amorphous state as it is cooled after being heated. Since a phase change material in a crystalline state has a low resistance and a phase change material in an amorphous state has a high resistance, the crystalline state may be defined as a set state or a logic level “0”, and the amorphous state may be defined as a reset state or a logic level “1”.
In order to reduce a chip size in a nonvolatile memory device including a PRAM, a large number of local bit lines are simultaneously discharged during read and write operations, and in this case, the local bit lines being simultaneously discharged have large capacitances. In the process of simultaneously discharging the local bit lines having large capacitance values, ground noises may greatly bounce. Also, the greatly bouncing ground noises may cause a peripheral circuit region included in the nonvolatile memory device to malfunction.